1. Field of the Invention
The present invention relates to a wire dot impact printer apparatus, in particular, a wire motion detecting apparatus for a wire dot head.
2. Description of the Related Art
In a wire dot impact printer apparatus, a wire dot head is disposed opposite to a platen through an ink ribbon and a printing medium. A printing wire is banged on the printing medium through the ink ribbon.
With a wire motion detecting apparatus that detects the motion of the printing wire dot head, the wire dot impact printer apparatus prints data on various printing mediums. In reality, in the printer apparatus, the thickness of a printing medium for use (or the number of copy papers) is detected by the wire motion detecting apparatus and a sensor circuit of a print time detecting portion. When the thickness of the printing paper is changed, the distance between the forward edge of the wire dot head and the printing medium (this distance is referred to as head gap) is optimally adjusted.
However, in the wire motion detecting apparatus for the conventional wire dot head, if a velocity wave form V.sub.1 is abnormal or if a sensor failure takes place, a motion time T.sub.S, a print time T.sub.P, and a return time T.sub.R cannot be precisely measured.